In this article we will discuss about the diseases of fish:- 1. Bacterial Diseases 2. Fungal Diseases 3. Viral Diseases 4. Protozoan Diseases 5. Disease Caused by Trematodes.
Bacterial Diseases:
1. Fin and Tail Rot:
White line on the margin of the fin; fin rays become brittle and start breaking.
Treatment:
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1 minute dip treatment in 500 ppm copper sulphate solution.
2. Furunculosis:
Open sores or ulcers on the body.
Treatment:
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Dip treatment for 1 minute in 1 : 2000 copper sulphate solution for 3-4 days.
3. Dropsy:
Accumulation of fluid inside the body cavity; scale protrusion; exophthalmic condition.
Treatment:
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Dip treatment in 5 ppm potassium permanganate solution for 2 minutes.
4. Eye Disease:
Cornea of eye becomes vascularised and later becomes opaque; eyeball gets decayed.
Treatment:
Chloromycetin (8-10 mg/ litre) bath for 1 hour for 2-3 days.
Fungal Diseases:
Water-Mould Disease (Saprolegniasis):
Dies after ulceration or exfoliation of skin followed by haemorrhage; blindness; tufts of white hair-like out-growth in the affected region.
Treatment:
Dip treatment for 3 seconds in 1 : 10000 solution of malachite green or for 5-10 minutes in 3% common salt solution or 1 : 1000 solution of potassium permanganate.
Viral Diseases:
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1. Viral Haemorrhagic Septicaemia (VHS):
Anaemia; pale discolouration of gill; swelling of eyes and belly; oedema of muscles; inflammation of intestine; anus becomes protruded.
Treatment:
No known cure for VHS. Prevention is the best approach to control like other viral diseases. Contaminated water should be thoroughly disinfected before use.
Protozoan Diseases:
1. Ichthyophthiriasis (White-Spot Disease):
Small whitish-cysts of about 1 mm diameter on the skin, gills and fins.
Treatment:
5 days bathing in 2 ppm methylene blue; hourly dip treatment in 1 : 5000 formalin solution for 7-10 days.
2. Knot Disease:
Small knots in the skin of common carp.
Treatment:
All infected fish should be destroyed or burnt.
3. Boil Disease:
Large boils varying from the size of a nut to that of a hen’s egg on several parts of body.
Treatment:
Bath in 3% common salt solution or in 1 : 2500 formalin solution for 10 minutes.
4. Pox Disease:
Small milky-white spots raised 1-2 mm above the surface of skin.
Treatment:
Intra-peritoneal injection with 1 ml of a 1 % solution of arsenic compound, Arycil.
5. Costiasis:
Bluish-coating on the skin; lesions as irregular patches.
Treatment:
Bath in 3% common salt solution or in 1 : 2500 formalin solution for 10 minutes.
6. Whirling Disease:
Caudal bend, deformity of the oral region and blackening of tail region.
Treatment:
Destroy all infected fish by applying quicklime (pond disinfectant) at the rate of 2 t/ha.
Disease Caused by Trematodes:
1. Gyrodactylosis Dactylogyrosis:
Fading of colours; drooping of scales; peeling of skin.
Treatment:
Dip treatment in 5% common salt solution or in 1 : 5000 formalin solution for 5 minutes.
2. Diplostomiasis (Black-Spot Disease):
Small black nodules of about 1-5 mm diameter in the affected region.
Treatment:
Dip treatment in 3 : 100000 picric acid for 1 hour; Di-n-butyl tin oxide at the rate of 250 mg/kg body weight.
3. Worm Cataract:
Whitish-eye due to the white dots, i.e. little worms situated between lens and lens capsule.
Treatment:
Dip treatment in potassium antimonyl tartrate (1.5 mg/litre).